#include <SlippyMap.h>
#include <math.h>
#include <QNetworkCacheMetaData>

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif


uint qHash(const QPoint& p)
{
    return p.x() * 17 ^ p.y();
}

// tile size in pixels
const int tdim = 256;

QPointF tileForCoordinate(qreal lat, qreal lng, int zoom)
{
    qreal zn = static_cast<qreal>(1 << zoom);
    qreal tx = (lng + 180.0) / 360.0;
    qreal ty = (1.0 - log(tan(lat * M_PI / 180.0) + 1.0 / cos(lat * M_PI / 180.0)) / M_PI) / 2.0;
    return QPointF(tx * zn, ty * zn);
}

qreal longitudeFromTile(qreal tx, int zoom)
{
    qreal zn = static_cast<qreal>(1 << zoom);
    qreal lat = tx / zn * 360.0 - 180.0;
    //qDebug() << lat;
    return lat;
}

qreal latitudeFromTile(qreal ty, int zoom)
{
    qreal zn = static_cast<qreal>(1 << zoom);
    qreal n = M_PI - 2 * M_PI * ty / zn;
    qreal lng = 180.0 / M_PI * atan(0.5 * (exp(n) - exp(-n)));
    //qDebug() << lng;
    return lng;
}

SlippyMap::SlippyMap(QObject *parent) : QObject(parent){
    width = 400;
    height = 300;
    zoom = 12;
    latitude = 34.7249;
    longitude = -86.6412;
    m_emptyTile = QPixmap(tdim, tdim);
    m_emptyTile.fill(Qt::lightGray);
    metaData = new QNetworkCacheMetaData;
    QDateTime dateTime;
    QDate date;
    QTime time;
    time.setHMS(1,1,1,1);
    date.setYMD(QDate::currentDate().year()+10,1,1);
    dateTime.setDate(date);
    dateTime.setTime(time);
    cache = new QNetworkDiskCache;
    metaData->setSaveToDisk(true);
    metaData->setExpirationDate(dateTime);
    cache->updateMetaData(*metaData);
    cache->setCacheDirectory("cache");
    cache->setMaximumCacheSize(22147483647);
    m_manager.setCache(cache);
    connect(&m_manager, SIGNAL(finished(QNetworkReply*)), this, SLOT(handleNetworkData(QNetworkReply*)));
    qDebug() << "Cache location: " << cache->cacheDirectory();
    qDebug() << "Max cache size: " << cache->maximumCacheSize();
    qDebug() << "Current cache size: " << cache->cacheSize();
    qDebug() << "Space left: " << cache->maximumCacheSize()-cache->cacheSize();
    qDebug() << "Cache expires on : " << dateTime;

}


void SlippyMap::invalidate() {
    if (width <= 0 || height <= 0)
        return;

    QPointF ct = tileForCoordinate(latitude, longitude, zoom);
    qreal tx = ct.x();
    qreal ty = ct.y();

    // top-left corner of the center tile
    int xp = width / 2 - (tx - floor(tx)) * tdim;
    int yp = height / 2 - (ty - floor(ty)) * tdim;

    // first tile vertical and horizontal
    int xa = (xp + tdim - 1) / tdim;
    int ya = (yp + tdim - 1) / tdim;
    int xs = static_cast<int>(tx) - xa;
    int ys = static_cast<int>(ty) - ya;

    // offset for top-left tile
    m_offset = QPoint(xp - xa * tdim, yp - ya * tdim);

    // last tile vertical and horizontal
    int xe = static_cast<int>(tx) + (width - xp - 1) / tdim;
    int ye = static_cast<int>(ty) + (height - yp - 1) / tdim;

    // build a rect
    m_tilesRect = QRect(xs, ys, xe - xs + 1, ye - ys + 1);

    if (m_url.isEmpty())
        download();

    emit updated(QRect(0, 0, width, height));
}


void SlippyMap::render(QPainter *p, const QRect &rect) {
    for (int x = 0; x <= m_tilesRect.width(); ++x)
        for (int y = 0; y <= m_tilesRect.height(); ++y) {
            QPoint tp(x + m_tilesRect.left(), y + m_tilesRect.top());
            QRect box = tileRect(tp);
            if (rect.intersects(box)) {
                if (m_tilePixmaps.contains(tp))
                    p->drawPixmap(box, m_tilePixmaps.value(tp));
                else
                    p->drawPixmap(box, m_emptyTile);
            }
        }
}



void SlippyMap::pan(const QPoint &delta) {
    QPointF dx = QPointF(delta) / qreal(tdim);
    QPointF center = tileForCoordinate(latitude, longitude, zoom) - dx;
    latitude = latitudeFromTile(center.y(), zoom);
    longitude = longitudeFromTile(center.x(), zoom);
    invalidate();
}


void SlippyMap::handleNetworkData(QNetworkReply *reply) {
    QImage img;
    QPoint tp = reply->request().attribute(QNetworkRequest::User).toPoint();
    if (!reply->error())
        if (!img.load(reply, 0))
            img = QImage();
    reply->deleteLater();
    m_tilePixmaps[tp] = QPixmap::fromImage(img);
    if (img.isNull())
        m_tilePixmaps[tp] = m_emptyTile;
    emit updated(tileRect(tp));

    // purge unused spaces from memory.. commented out for now.
  /*  QRect bound = m_tilesRect.adjusted(-2, -2, 2, 2);
    foreach(QPoint tp, m_tilePixmaps.keys())
    if (!bound.contains(tp))
        m_tilePixmaps.remove(tp);
*/

    QVariant fromCache = reply->attribute(QNetworkRequest::SourceIsFromCacheAttribute);
    if(fromCache.toBool() == 0){
        qDebug() << "Image not cached, downloading now.";
    }

    download();
}



void SlippyMap::download() {
    QPoint grab(0, 0);
    for (int x = 0; x <= m_tilesRect.width(); ++x)
        for (int y = 0; y <= m_tilesRect.height(); ++y) {
            QPoint tp = m_tilesRect.topLeft() + QPoint(x, y);
            if (!m_tilePixmaps.contains(tp)) {
                grab = tp;
                break;
            }
        }
    if (grab == QPoint(0, 0)) {
        m_url = QUrl();
        return;
    }

    QString path = "http://tile.openstreetmap.org/%1/%2/%3.png";
    m_url = QUrl(path.arg(zoom).arg(grab.x()).arg(grab.y()));
    //qDebug() << m_url;
    QNetworkRequest request;
    request.setUrl(m_url);
    request.setRawHeader("User-Agent", "ZephyrAPRS");
    request.setAttribute(QNetworkRequest::User, QVariant(grab));
    m_manager.get(request);
}


QRect SlippyMap::tileRect(const QPoint &tp) {
    QPoint t = tp - m_tilesRect.topLeft();
    int x = t.x() * tdim + m_offset.x();
    int y = t.y() * tdim + m_offset.y();
    return QRect(x, y, tdim, tdim);
}
